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The first known mass extinction was the Great Oxidation Event 2.4 billion years ago, which killed most of the planet's obligate anaerobes. Researchers have identified five other major extinction events in Earth's history, with estimated losses below: [11] End Ordovician: 440 million years ago, 86% of all species lost, including graptolites
The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
Depending on the continent, the era generally falls between the years AD 200–600 and AD 1200–1500. The major classical civilizations that the era follows are Han China (ending in 220), the Western Roman Empire (in 476), the Gupta Empire (in the 550s), and the Sasanian Empire (in 651). Middle Ages – Lasted from the 5th to the 15th century.
All life on Earth can be traced back to a Last Universal Common Ancestor, or LUCA. A new study suggests that this organism likely lived on Earth only 400 million years after its formation.
Dating back to Anaxagoras in the 5th century BC, panspermia [29] is the idea that life originated elsewhere in the universe and came to Earth. The modern version of panspermia holds that life may have been distributed to Earth by meteoroids , asteroids , comets [ 30 ] or planetoids . [ 31 ]
The start and end of a new generation is sometimes vague, but these generation group names are often used for individuals born between the following years: Greatest Generation: 1901-1927. Silent ...
They first appeared in the fossil record around 66 million years ago, soon after the Cretaceous–Paleogene extinction event that eliminated about three-quarters of plant and animal species on Earth, including most dinosaurs. [25] [26] One of the last Plesiadapiformes is Carpolestes simpsoni, having grasping digits but not forward-facing eyes.
With the start of a new year on Jan. 1, 2025, comes the emergence of a new generation. 2025 marks the end of Generation Alpha and the start of Generation Beta, a cohort that will include all ...